iwlwifi: msix: limit max RX queues for 9000 family

There is an issue in the HW DMA engine in the 9000 family of devices
when more than 6 RX queues are used.  The issue is that the FW may
hang when IWL_MVM_RXQ_NSSN_SYNC notifications are sent.

Fix this by limiting the number of RX queues to 6 in the 9000 family
of devices.
Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200911204056.37d90f9ceb0c.I8dfe8a7d3a7ac9f0bc9d93e4a03f8165d8c999d2@changeidSigned-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/iwl-trans.h

@@ -316,6 +316,7 @@ static inline void iwl_free_rxb(struct iwl_rx_cmd_buffer *r)
 #define IWL_MGMT_TID		15
 #define IWL_FRAME_LIMIT	64
 #define IWL_MAX_RX_HW_QUEUES	16
+#define IWL_9000_MAX_RX_HW_QUEUES	6
 
 /**
  * enum iwl_wowlan_status - WoWLAN image/device status

drivers/net/wireless/intel/iwlwifi/pcie/trans.c

@@ -1607,11 +1607,15 @@ iwl_pcie_set_interrupt_capa(struct pci_dev *pdev,
 	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
 	int max_irqs, num_irqs, i, ret;
 	u16 pci_cmd;
+	u32 max_rx_queues = IWL_MAX_RX_HW_QUEUES;
 
 	if (!cfg_trans->mq_rx_supported)
 		goto enable_msi;
 
-	max_irqs = min_t(u32, num_online_cpus() + 2, IWL_MAX_RX_HW_QUEUES);
+	if (cfg_trans->device_family <= IWL_DEVICE_FAMILY_9000)
+		max_rx_queues = IWL_9000_MAX_RX_HW_QUEUES;
+
+	max_irqs = min_t(u32, num_online_cpus() + 2, max_rx_queues);
 	for (i = 0; i < max_irqs; i++)
 		trans_pcie->msix_entries[i].entry = i;